The invention relates to a storage system and a path switching method, and particularly relates to a technique of performing backup or restoration of data using an externally-connected storage apparatus.
A conventional example of a virtual disk library apparatus for replicating data from a general computer called a business server is a virtual disk library apparatus using: a tape library apparatus using a magnetic tape cartridge or a logical volume provided in a storage area of a physical volume.
Also, there is a virtualization apparatus that is connected between a business server and a virtual disk library apparatus and provides the business server with a virtual logical volume (hereinafter simply referred to as “virtual volume”) in a storage area of a physical disk.
A method for backing up data from a business server by utilizing the above apparatuses is as follows. First, data from a business server is stored in a logical volume created in a storage area of a physical disk (hereinafter referred to as “logical volume”) provided in a virtualization apparatus. Then, the data in the logical volume is replicated in another logical volume on a per-volume basis by backup processing. The replicated data from the data is stored in a virtual volume, but is actually stored in a logical volume in a virtual disk library apparatus externally connected to the virtualization apparatus.
Here, backup processing needs to be performed for plural generations with the purpose of protecting data and improving reliability. Backup processing is generally executed on an inexpensive tape library apparatus. As described above, replicated data is stored in a tape library apparatus via a virtualization apparatus.
Incidentally, a technique is disclosed in JP 11-242570 A in which: a magnetic disk apparatus using a magnetic disk and a tape library apparatus are stored in a virtual disk library apparatus; and data backup and data restoration are performed between the magnetic disk apparatus and the tape library apparatus to achieve capacity management for data storage and promotion of access efficiency.
Moreover, a technique is disclosed in JP 2002-259063 A in which: a single communication port for conducting data transfer between a host and a storage control apparatus, cache memory for storing control information and data from the host, a storage apparatus composed of disk devices, etc. for storing data from the host, and a control unit for controlling the communication port, the cache memory, and the storage apparatus are provided; and communication processing is multiplexed in a port control unit having the communication port, or switching of communication ports is conducted depending on circumstances, thereby executing communication processing.
However, in conventional backup processing, the virtualization apparatus and the tape library apparatus must be connected to each other via a dedicated path of a dedicated port due to a characteristic that the tape library apparatus conducts data write sequentially.
Also, in conventional backup processing, backup processing from the virtualization apparatus to the tape library apparatus is executed after the completion of backup processing from the business server to the virtualization apparatus.
Therefore, in conventional backup processing, the dedicated port for connecting the virtualization apparatus with the tape library apparatus cannot be used in backup processing from the virtualization apparatus to the tape library apparatus, and the dedicated port for connecting the business server with the virtualization apparatus cannot be used in backup processing from the business server to the virtualization apparatus.
Accordingly, conventional backup processing has a problem in that a data transfer band is not effectively used, which leads to reduced performance of the entire system. The same applies to restoration processing.